Mixer base



FIG. 1 is a perspective view of a mixer base showing my new design;

FIG. 2 is a front elevation view thereof;

FIG. 3 is a left side elevation view thereof;

FIG. 4 is a rear elevation view thereof;

FIG. 5 is a right side elevation view thereof; and,

FIG. 6 is a top view thereof.

The broken lines shown in FIGS. 1-6 are for illustrative purposes only and form no part of the claimed design. 

The ornamental design for a mixer base, as shown and described. 